Carranteane is a variant way of writing Carrownteeaun, so if your Dad grew up there, you and I are undoubtedly related, because that's the townland where my grandfather, James Peter Gallagher, grew up (he was born there one year after your James McNicholas died in 1883).
My Gallagher's (in both Carrownteeaun and Comderry) married a number of McNicholas's in the 19th century. One of my grandfather's aunts was a McNicholas, as was one of his sisters-in-law (on his wife's side), and so were several cousins of his father, Peter Gallagher). I can't prove it on paper, but I suspect that my Gallagher branch moved to Carrownteeaun from Comderry as a result of a marriage with a McNicholas, and if so that would mean that my great-grandfather Peter's mother (whose name I don't know) was a-McNicholas from Carrownteeaun. The Carrownteeaun area McNicholas's also had family just across the parish boundary to the north in Bohola parish (especially in the townland of Altbaun).
With respect to my great-grandfather. Peter Gallager, and his three (known) siblings, about one-third of their children had at least one McNicholas as a baptismal sponsor, so the intertwined Gallagher-McNicholas familial relationship in and around Carrownteeaun (and later in St. Louis and New York) is pretty significant.
Several Kilgallon's also acted as sponsors at baptisms in my family, including one who I asssume was the Mary Kilgallon whom you mentioned, so I suspect that they are also cousins of some kind. The James McNicholas and Mary Kilgallon whom you mentioned had a daughter named Bridget who was born in Carrownteeaun in 1873, who I suspect was a second cousin of my grandfather.
The Cuillalea-Comderry-Carrownteeaun connection among the Gallagher's, McNicholas's and Kilgallon's also seems very likely. There was a Thady Gallagher in Comderry, probably a second cousin of my great-grandfather, who married a Catherine McNicholas in 1865, and I think that Mary Kilgallon was once again a sponsor at the baptism of one of their children (her surname is hard to read in the register).
If youve done DNA testing, we might compare results. My results are posted at GEDMATCH, and my kit number is T780556.